/*
 * Copyright 2011 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.peterkuterna.android.apps.devoxxsched.util;

import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * Provides static methods for creating mutable {@code Set} instances easily and
 * other static methods for working with Sets.
 * 
 */
public class Sets {

	/**
	 * Creates an empty {@code HashSet} instance.
	 * 
	 * <p>
	 * <b>Note:</b> if {@code E} is an {@link Enum} type, use
	 * {@link EnumSet#noneOf} instead.
	 * 
	 * <p>
	 * <b>Note:</b> if you only need an <i>immutable</i> empty Set, use
	 * {@link Collections#emptySet} instead.
	 * 
	 * @return a newly-created, initially-empty {@code HashSet}
	 */
	public static <K> HashSet<K> newHashSet() {
		return new HashSet<K>();
	}

	/**
	 * Creates a {@code HashSet} instance containing the given elements.
	 * 
	 * <p>
	 * <b>Note:</b> due to a bug in javac 1.5.0_06, we cannot support the
	 * following:
	 * 
	 * <p>
	 * {@code Set<Base> set = Sets.newHashSet(sub1, sub2);}
	 * 
	 * <p>
	 * where {@code sub1} and {@code sub2} are references to subtypes of
	 * {@code Base}, not of {@code Base} itself. To get around this, you must
	 * use:
	 * 
	 * <p>
	 * {@code Set<Base> set = Sets.<Base>newHashSet(sub1, sub2);}
	 * 
	 * @param elements
	 *            the elements that the set should contain
	 * @return a newly-created {@code HashSet} containing those elements (minus
	 *         duplicates)
	 */
	public static <E> HashSet<E> newHashSet(E... elements) {
		int capacity = elements.length * 4 / 3 + 1;
		HashSet<E> set = new HashSet<E>(capacity);
		Collections.addAll(set, elements);
		return set;
	}

	/**
	 * Creates a {@code SortedSet} instance containing the given elements.
	 * 
	 * @param elements
	 *            the elements that the set should contain
	 * @return a newly-created {@code SortedSet} containing those elements
	 *         (minus duplicates)
	 */
	public static <E> SortedSet<E> newSortedSet(E... elements) {
		SortedSet<E> set = new TreeSet<E>();
		Collections.addAll(set, elements);
		return set;
	}

}
